Transcript User Agent Server - School of Information Technology

LIDO Telecommunications Essentials®
Part 3
Next Generation Networks
IP Services
LIDO
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Contents
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IP Telephony, unified messaging, applications
RTP, Multimedia
VOIP QoS revisited
Signaling protocols, ENUM
VPNs
IPTV revisited
LIDO
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Value Added IP Applications
• Evolving next-generation IP services include
LIDO
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IP virtual private networks (VPNs),
IP telephony (IPT) and Voice over IP (VoIP),
IP centrex and IP call centers,
application hosting,
mobility management/follow-me services,
unified messaging,
instant messaging (IM),
presence management,
Video over IP,
Internet Protocol TV (IPTV),
and audioconferencing, videoconferencing, and
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IP Telephony (IPT) Definitions
• There are three main categories of telephony or
voice communications over IP networks, according
to the ITU-T.
• Internet Protocol Telephony (IPT)
– The transmission of voice, fax and related
services over packet-switched IP-based
networks.
• Internet Telephony
– Telephony in which the principal transmission
network is the public Internet.
• Voice over IP (VoIP)
– IP Telephony, in which the principal transmission
network or networks are private, managed IP- 4
LIDO
based networks
Is IP Telephony Here?
• Not all enterprises are using or considering IP
Telephony services, but a large percentage are
using or considering migrating to MPLS, in part
because combining voice, video, and data can
finally cost justify MPLS.
• Most organizations are currently using
predominantly ATM or Frame Relay, with some
IP VPNs here and there.
LIDO
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IPT Network Taxonomy
Application Layer
Application
Platform
App-Specific
Call Processing
Protocols
Intra-app Protocols
TAPI,
JTAPI, etc.
H.323, SIP, Others
Signaling Layer
Media Layer
LIDO
Signaling
Platform
Bearer
Platform
Signaling Protocols
TDM,
Frame Relay, ATM
Media/Bearer
Control Protocols
MGCP,
Megaco
Media Transport
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Legacy Support
IP terminal adapters for
standard telephones
LIDO
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IP Hardphones
LIDO
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IP Softphones
LIDO
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IP Webphones
LIDO
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SIP Phones
LIDO
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Mobile IP Devices
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LIDO
3G handsets
Wi-Fi SIP phones
PDAs
Game platforms
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IP PBXs
Application Areas
• Significant progress has been made in
several key applications areas
– Unified messaging
– Conferencing applications
– Collaboration applications
– Presence awareness
– Multimedia packages
– Mobility features
– Extensible SIP support
LIDO
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IP PBXs
Application Areas
• The most notable trends include
– Video is coming to your desktop
– Document collaboration
– Mobility
LIDO
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IP PBXs : Key Collaboration and
Conferencing Features
– Softphone support
– Use of presence (dynamic
and/or static)
– Mobility features
– Conferencing (scheduled
and/or ad hoc)
– Search capabilities
– Contacts/database access,
integration
– Video point-to-point,
conferencing
– Call control: of external
devices
LIDO
– Call control: filters, find
me/follow me
– Recent-call history, sort, quick
dial
– Instant messaging
– Chat; multiparty IM
– Document viewing,
presentation
– Document collaboration,
coediting
– Whiteboarding
– Web co-browsing
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IP PBXs :
Key Unified Messaging Features
– Redundant voice mail servers
– Text-to-Speech readout of
email, in multiple languages
– Automatic speech recognition
(ASR)
– Inbox shows caller by ANI
number and/or name
– Voice/email shows message
duration
– Can reply, forward
voice/email
– Can add other attachments
– Can send voice/email via
distribution list
LIDO
– Can send voice/email via
distribution list
– Telephony User Interface
(TUI)-based retrieval of
voice/email
– Call-out off-system voice mail
delivery
– Voice mail notification options
– Scheduled delivery of voice
mails
– Can dial-back from Inbox
interface
– Mobility features
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Standards for IP Voice
• Voice traffic characteristics
– Isochronous traffic flow
– Real-time communications
– Delay-sensitive
– Loss-sensitive
– Low bandwidth requirements
– High Quality of Service requirement
LIDO
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Delay and Voice Quality
• Delay can result in serious degradation of
voice quality, and needs to be tightly
controlled in packet networks.
• Delay Standards – ITU recommendations
– voice – 150 msec max end-to-end
– Video - 80 msec max end-to-end
– interactive apps - 30-50 msec max, end-to-end
LIDO
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Delay and Voice Quality
• Sources of delay
– Device sample capture
– Encode delay
G.711/64 Kbps
Budget in ms
G.729/8 Kbps
Budget in ms
.1
2.5
.1
17.5
10
.5
30
5
10
.5
35
.5
.5
94.6
20
.5
30
5
10
.5
35
5
.5
124.1
• algorithmic delay + processing delay
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–
–
LIDO
Packetization/framing
Move to output queue/queuing delay
Access (up) link transmission
Backbone network transmission
Access (down) link transmission
Input queue to application
Jitter buffer
Decode processing delay
Device playout delay
TOTAL
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Media Transport
• Media transport protocols involved in moving
the bits include
– Realtime Transport Protocol (RTP)
– Secure Real-Time Protocol (SRTP)
• Feedback and statistics are supported via
– Realtime Transport Control Protocol (RTCP)
– RTCP XR (Reporting Extension)
LIDO
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VoIP Quality of Service
• “The problem we are trying to solve is to give
“better” service to some at the expense of
giving worse service to others – QoS
fantasies to the contrary, it’s a zero sum
game” (Van Jacobson)
• There are several techniques employed to
improve the network QoS.
LIDO
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VoIP QoS Mechanisms
• RED (Random Early Detect)
– On a shared voice/data queue, RED does not prevent
large delay and jitter for voice. RED is primarily effective
to avoid congestion.
• WFQ (Weighed Fair Queuing)
– Each flow gets the share of the server/link bandwidth in
proportion to its weight.
• RSVP (Reservation Resource Protocol)
– RSVP is the primary specification for handling multimedia
traffic over IP subnets. It enhances connectionless besteffort service by providing QoS requests and guarantees.
LIDO
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VoIP QoS Mechanisms
• IP Precedence
– “Poor man’s” approach to QoS. Sets IP
Precedence/DSCP higher on voice packets, putting them
in a different queue, resulting in isolation from best effort
traffic.
• DiffServ
– A small bit-pattern in each packet, the Diffserv Code Point
(DSCP), is used to mark a packet to receive a particular
forwarding treatment, or per-hop behavior, at each
network node.
LIDO
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VoIP QoS Mechanisms
• CRTP (Compressed RTP)
– Involves RTP compression, reducing the
traditional 40 byte header to 2-4 bytes.
• MCML (Multi-Class Multi-Link PPP)
– MCML allows multiple fragment streams on a
multi-link PPP session, interleaving small (i.e.
voice) packets between the fragments of big
packets by applying WFQ at the fragment level.
LIDO
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VoIP Protocols - Call Signaling
• Original standard: H.323
– Complex
– Very bad scaling properties
• Centralized control: Media Gateway Control
Protocol (MGCP)
– Simple: models current PSTN Call control architecture
• Decentralized control: Session Initiation Protocol
(SIP)
– Transaction based – good match for “stupid network”
paradigm
LIDO
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Scope of H.323
H.323
Terminal
H.323
Terminal
H.323 Architecture
V.70
Terminal
PSTN
H.323
MCU
H.323
Gatekeeper
LIDO
WAN
RSVP
H.323
Terminal
H.324
Terminal
Speech
Terminal
H.323
Gateway
ISDN
H.320
Terminal
Speech
Terminal
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H.323
• H.323 strengths
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ITU standards-based
Mature protocol with many large scale deployments
Wide spread vendor support and market acceptance
Facilitates interoperability between vendors
Defined standards for supplementary services
Network retains call state for duration of call, greater call control
Application services available through gatekeeper and best of breed
application platforms
• H.323 limitations
– Maintaining call state in the network increases costs to scale
– Limited deployment of softphones, many are proprietary
– Modeled after network layer standards
LIDO
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Megaco and MGCP
• Both the Megaco (Media Gateway Controller) and
MGCP (Media Gateway Control Protocol) protocols
are for control of elements in a physically
decomposed multimedia gateway, which enables
separation of call control from media conversion.
• Both Megaco and MGCP are media/device control
protocols.
• They both embrace a philosophy in which the
network is smart and the endpoint is dumb.
• Services are provided by intelligent network
elements.
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LIDO
Megaco and MGCP
MGC
or Call Agent
or Softswitch
SIGtrans
Global Signaling
MGCP,
H.248/Megaco
H.323
SIP
One Logical
VoIP Gateway
SS7,
ISDN
Q.Sig
LIDO
PSTN Bearer
Media
Gateway
Signaling
Gateway
MGC
Media Transport
T1/E1/PRI
OCx
E&M
Media
Gateway
RTP/UDP/IP
ATM AAL1,2,5
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Session Initiation Protocol (SIP)
SIP
LAN A
SIP
SIP
SIP
LAN B
•Client-Server Model
•User Agent Client (UAC) – Initiates sessions
•User Agent Server (UAS) – Responds to session requests
•User Agent = UAC + UAS
LIDO
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SIP
• SIP is an application-layer control protocol
that can establish, modify, and terminate
multimedia sessions.
• SIP can also invite participants to already
existing sessions, such as multicast
conferences.
• Media can be added to and removed from an
existing session.
LIDO
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SIP
• SIP supports five facets of establishing and
terminating multimedia communications:
LIDO
– User location: determination of the end system to be used
for communication;
– User availability: determination of the willingness of the
called party to engage in communications;
– User capabilities: determination of the media and media
parameters to be used;
– Session setup: "ringing", establishment of session
parameters at both called and calling party;
– Session management: including transfer and termination
of sessions, modifying session parameters, and invoking
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services.
SIP
• SIP is a component that can be used with other
IETF protocols to build a complete multimedia
architecture, such as
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Real-time Transport Protocol (RTP)
Real-Time Streaming Protocol (RTSP)
Media Gateway Control Protocol (Megaco)
Session Description Protocol (SDP)
• Therefore, SIP should be used in conjunction with
other protocols in order to provide complete
services to the users.
LIDO
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SIP Network Elements
• Basic SIP elements include user agents,
proxies, registrars, and redirect servers.
• User agents usually, but not necessarily,
reside on a user's computer in the form of an
application
• User agents are often referred to as User
Agent Server (UAS) and User Agent Client
(UAC).
LIDO
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SIP Proxy Server
User
Agents
User Agent
IP-Based
Network
Proxy
Server
LIDO
•Optional SIP component
•Handles routing of SIP Signaling
•Does not initiate SIP messages
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SIP Registrar Server
User
Agents
User Agent
IP-Based
Network
Registrar
Server
LIDO
•Optional SIP component
•Does not route SIP messages
•Handles registration from SIP UAs
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SIP Redirect Server
User
Agents
User Agent
IP-Based
Network
Redirect
Server
LIDO
•Optional SIP component
•Does not route SIP messages
•Returns a redirect to UA for direct routing
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SIP and Presence
• What is Presence?
– Ability,willingness, desire, and capability of a user
to communicate across media and devices, and
even time and space.
– Presence systems collect and distribute
presence information to interested parties
– Policy is central to presence
– The value of presence is exponential with the
richness of the data it has access to.
LIDO
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SIP and Presence
• Presence has great value in improving the
productivity an an organization.
• Accuracy is paramount to presence.
• Productivity enhancement depends on
accurate presence data.
• There are also arguments against presence.
• Standards, privacy and security are
concerns.
LIDO
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Electronic Number Mapping
(ENUM)
• What is the issue
– How do you find a telephone (number) on the Internet?
– How do you find islands of connectivity across domain
boundaries?
• ENUM will assist in the convergence of the Public
Switched Telephone Network (PSTN) and the IP
network
– it is the mapping of a telephone number from the PSTN to
Internet services--telephone number in, URL out.
LIDO
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ENUM Steps
Take the phone number
+1-415-555-1212
Turn it into a FQDN 2.1.2.1.5.5.5.5.1.4.1.E164.arpa
(Fully Qualified Domain Name)
Ask the DNS
mailto:[email protected]
Return a list of URIs sip:[email protected]
LIDO
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ENUM Possibilities
• Because ENUM puts telephone numbers into
the DNS, it allows for a wide range of
applications based solely on a phone
number.
• Along with VoIP, other applications include
addressing for fax machines, e-mail, instant
messaging, and web sites. The possibilities
are enormous.
LIDO
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Virtual Private Network
Hong
Kong
Corp
Dial-up
Dubai Center
Leased Lines
VPN
Circuit-switched or
Packet-switched
San Francisco.com
Remote Access Workers
Dial-up
San Francisco.com
London Times
Mobile Users
LIDO
London Times
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Virtual Private Networks
• VPNs isolate customer traffic on shared service
provider facilities.
– Enterprise’s traffic is aggregated with other traffic.
– VPNs have been around since X.25 closed user groups
and AT&T software-defined networks
– VPNs look like a private network but actually run across
either the public circuit switched network or public packet
switched data networks
• VPN is a concept, not a specific set of technologies
LIDO
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Customer Edge Model
• Customer-based
– Requires CPE to be fully capable of configuring and
provisioning the VPN, and thereby results in higher
passthrough operating expenses for the enterprise user.
– Routing intelligence resides at an end-user site.
– Carriers install gateways, routers and other VPN
equipment on the customer’s premises.
– As this requires the carrier to manage on-site equipment,
the costs associated with the on-site visits from field
engineers can be high.
– Preferred where customer desires to have control over all
aspects of security.
LIDO
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Provider Edge Model
• Provider-based
– VPN “intelligence” resides at the provider’s edge, where it
can be extended out to many end-user locations.
– Carriers house all necessary equipment at a point of
presence near the customer’s location.
– Offer the advantages of scalability, support for an
increasingly diverse range of IP-based services and
efficient prioritization of traffic.
– Provide the foundation needed to integrate fixed and
mobile VPN communications into one seamless
framework.
– Preferred by customers who wish to take advantage of
the carrier’s VPN economies of scale.
LIDO
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VPN Categories
• There are three main categories of VPNs
– Internet-based
– Provisioned
– IP
LIDO
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Internet-based VPN
Customer
Location 1
INTERNET
Tier 2/3
ISP
Peering Point
Customer
Location 2
LIDO
Tier 2/3
ISP
Peering Points
Tier 1
ISP
Tier 2/3
ISP
Internet Exchange,
Network Access Points
(NAPs)
Tier 1
ISP
Tier 2/3
ISP
Customer
Location 3
Peering Point
Customer
Location 4
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Internet-based VPN
Remote Users
Dial-up
To ISP POP
Internet or
IP backbone
Laptops & PC’s With
Client VPN Encapsulation
and Security Software
or Token Cards
Leased Line To ISP POP
CSU/DSU
Users
Leased Line
To ISP POP
Router
Firewall
CSU/DSU
Remote Site
Users
Router
Firewall
Servers
Servers
LIDO
VPN Server
Authentication
& Access Control
Server
VPN Server
(encapsulation
& security)
Authentication
& Access Control
Server
(RADIUS)
Central Site
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Provisioned VPN
Customer
Location 1
Service Provider Network
Customer
Location 3
Virtual Circuits (VCs)
between locations
Frame Relay, ATM
backbone
Customer
Location 2
LIDO
To Internet
Customer
Location 4
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Provisioned VPN
Remote Users
Dial-up
To Internet POP
Service Provider POP
Remote
Access Device
Laptops & PC’s With
Client VPN Encapsulation
and Security Software
or Token Cards
FR or ATM VC
FR or ATM VC
Multiservice
Access Device
Service Provider POP
CSU/DSU
Private Line,
FR or ATM VC
Router or
Integrated Access
Device
LAN
Traffic
LIDO
SNA
Traffic
Service
Provider
Network
Management
Service Provider POP
Multiservice
Access Device
Remote Site
Service
Provider
Service Provider
Core
Network Core
FR or ATM Virtual Circuit (VC)
Voice
Traffic
Packet Classification,
Priority & Bandwidth
Management Done Here.
Other
Traffic
Types
Central Site
CSU/DSU
Router or
Integrated Access
Device
LAN
Traffic
SNA
Traffic
Voice
Traffic
Customer Access to
Network Management
Other
Traffic
Types
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IP VPNs
• Definition: An IP VPN is basically a private,
or restricted, communications network
constructed over shared IP-based networks,
usually serviced on the providers' backbones,
but with connections to the public Internet.
• IP-based VPNs have traditionally been
referred to as networks of secure links over a
public IP infrastructure.
LIDO
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IP VPNs
• Today, there are three basic types of carriermanaged IP VPN services being offered
– CPE-based IPSec VPN
• Site-to-site enterprise VPN
• Gold standard for VPN security, especially when traffic is running
over the public Internet
– Network-based IPSec VPN
• May run over the Internet or the service provider’s private IP
facilities
• Customers use leased-line connections from the premises router
to the service provider’s POP (point of presence)
– Network-based MPLS or Virtual Router IP VPN services
LIDO
• Receiving the most attention today
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Tunneling
Internet
Encrypted
Tunnels
LIDO
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Tunneling
Server to Server
VPN Tunnel
Internet
Notebook
and Modem
LIDO
T1
HQ
Office
T1
Client to Server
VPN Tunnel
Remote
Office
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VPN Applications
• There are three main applications for
VPNs
–Intranets
–Remote Access VPNs
–Extranets
LIDO
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Intranet
Firewall
Mail Server
Router to ISP
Field Sales
Field Sales
Web Proxy Server
Internet
IP backbones
FR, ATM, MPLS
Web Server
Branch Office
Router
Internal
Remote Access
LAN
Internal network
External network
LIDO
Router
Server (RAS)
User User
Laser
Printer
Headquarters
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Remote Access VPNs
Local
ISP
VPN
Client
Headquarters
VPN
Server
Public
Network
Internal LAN
LIDO
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Extranet
Partner A
Partner B
Server 1
Server 2
Internet
IP Backbones
FR,ATM,MPLS
User on Server 2
Firewall/
Router/
VPN
Gateway
Firewall/
Router/
VPN
Gateway
User on Server 2
User on Server 2
LIDO
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IP VPN Taxonomy
Dial
PPP
L2TP
IPsec
LIDO
IP VPN
User-to-Site
Broadband
Cable/DSL
802.11
IPsec
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IP VPN Taxonomy
IP VPN
Site-to-Site
CE-based
PE-based
L3VPN
L2VPN
IPsec
GRE
2547
LIDO
Virtual
Router
VPWS
VPLS
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IPsec VPN
Dial
Internet
IPsec
IPsec
VLANs
IPsec
Firewall
LIDO
Campus
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IPsec
• IPSec (IP Security) is the IETF protocol suite
addressing basic data integrity and security.
• It covers encryption, authentication, and key
exchange.
• IPsec emphasizes security by authenticating both
ends of the tunnel connection, negotiating the
encryption protocol and key for the encrypted session
and encrypting and decrypting the session
establishment data.
LIDO
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IPsec
• IPsec utilizes transport and tunnel modes.
• In transport mode, only the IP payload is encrypted.
There is no change to the original IP header.
– This is generally used between hosts or routers and also
in client/server VPNs.
• In tunnel mode, the entire IP datagram is encrypted;
the entire original packet is encapsulated in IPsec
and given a new IP header.
– This mode is generally used between gateways.
LIDO
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Generic Routing Encapsulation (GRE)
• IETF RFC 2784 and RFC 1702 specify the
GRE, or Generic Routing Encapsulation
protocol for using IP as both the delivery and
payload protocol.
• It is a simple, stateless protocol that allows
for the tunneling of IP in IP.
• GRE tunnels can be used to form VPNs,
connecting remote sites using private IP
addresses via a public network.
LIDO
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Virtual Router VPNs
• In Virtual Router (VR) VPNs, each virtual router
runs an instance of a routing protocol that is
responsible for disseminating VPN reachability
information between virtual routers.
• Customer routing is extended across the provider
network.
• The objective of a Layer 3 virtual router VPN is to
provide per-VPN routing, forwarding, QoS, and
service management capabilities.
LIDO
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Virtual Router VPNs
P
Router
VPN1
CE
CE
Provider Edge
Router (PE)
VR of
VPN 1
P
Provider
Router
Backbone
Router
PE
P
Router
VR of
VPN 1
VR of
VPN 2
CE
VPN2
VR to VR L3 Tunnel
LIDO
VPN1
FR, ATM, IP, MPLS
CE
Access Connection
VR of
VPN 1
CE
Provider Backbone
VR of
VPN 2
VPN2
PE
VR to VR L2 Link
CE-VR Exchange
Any Routing Protocol
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Virtual Private LAN Service (VPLS)
Logical Bridge
CE4
CE1
CE2
VPLS
PE
MPLS Backbone
VPLS
PE
LIDO
Point-point Pseudo-wires
VPLS
PE
CE5
CE3
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Virtual Private LAN Service (VPLS)
• The advent of the Internet and the resulting
productivity gain spurred by the adoption of new
technologies is resulting in a demand for increased
bandwidth and services.
• Virtual Private LAN Services (VPLS) with an
Ethernet infrastructure present the optimal solution
for carriers to roll out new services profitably.
• The benefits from reduced capital and operating
expenditures add up quickly to benefit the
bottomline.
LIDO
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IPTV
• IPTV delivers digital television service to a
subscriber using IP over a broadband
connection.
• IPTV holds great promise for telcos.
• IPTV is not just a replication of the passive
cable TV viewing environment.
• Most of the world's leading telecom providers
are either investigating or deploying IPTV.
LIDO
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IPTV
• IPTV supports both live TV (multicasting) and
VOD (stored video).
• IPTV is viewed on a TV and requires a settop box.
• The video content is usually in MPEG-2 TS
(Transport Stream) format, delivered via IP
Multicast.
• IPTV was specifically designed to deliver
high-quality content to a traditional TV
through the Internet.
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LIDO
IPTV
• Advantages of IPTV include
– Two-way capability
– Point-to-point distribution, which allows each viewer to
view individual broadcasts
– Stream control
• IPTV enables providers to offer more services over
the same pipe.
• Streaming media is an almost identical server-side
technology to IPTV, but it terminates on a PC rather
than on a TV.
LIDO
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IPTV
• With IPTV, a network operator controls the
whole path from the time they assemble the
content to the delivery of that content to the
consumer’s home.
• With traditional streaming, network operators
don’t have the same bandwidth control.
LIDO
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IPTV
• This need for end-to-end control has also affected
how IPTV is deployed.
• IPTV is being implemented by people who own the
entire network.
• IPTV is able to deliver full-screen, high-quality video
content, while streaming is most often still limited to
small-screen and relatively low-quality video.
• High-definition TV is going to set another
benchmark that streaming media might struggle
with.
LIDO
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IPTV
• For telcos in particular, IPTV presents a ripe
opportunity to establish a foothold in the
nascent online video distribution market.
• It’s about coming to the consumer with a
bundle of offerings.
• IPTV is really laying the foundation for the
future.
LIDO
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Content
Protection
Content Providers
Broadcast TV
Channels, PPV
Content Manager
IPTV
Architecture
Prerecorded
Content
Other Content
IP Services Network
IPTV Services
Mgmt &
Operations
Edge Servers
C
Content o
Distributionn
Server
t
e
n
IPTV Services
t
LIDO
Core
Packet-switched Network
backbone
IPTV Services
Manager Systems
VOD Server
IPTV Client
TV + Set-top Box
DSL
Edge
IPTV
Broadcast Server Network
IPTV Client
PC + Set-top Box
Cable
Access
Network
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LIDO Telecommunications Essentials®
IP Services
Lili Goleniewski
The LIDO Organization, Inc.
www. telecomessentials.com
+1-415-457-1800
[email protected]
Skypes ID: lili.goleniewski
Telecom Essentials Learning Center
www.telecomessentials.com
LIDO
Copyright © 2007- The LIDO Organization, Inc.
All Rights Reserved
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